That's exactly what I did. I made two L brackets and bolted to the existing seat mount. The current seat mounts aren't equal distance apart from the center line. So, I had to fab the brackets separately after centering the jump seat. You could do the same to the rear seat if you wanted to, however, I was not going to use it as a seat so I didn't. The added bonus of not mounting the rear part of the jump seat is that it folds up. This makes for easy cleaning under it and might just let people get to the 3rd row seat easier. But, who uses the 3rd row seats? I always have them down for added cargo space.
I put some gaffers tape on the underside of the carpet before I cut it just to help keep the fibers intact.